Field of the Invention
The invention generally relates to electronics, and in particular, to clock and data recovery.
Description of the Related Art
Electronic systems such as transceivers use clock and data recovery modules to acquire and track incoming signals. A clock and data recovery, or symbol timing recovery, module often uses an oversampled digital phase locked loop (DPLL) operating at a clock frequency much higher than a target data rate. A clock and data recovery system may be designed to acquire demodulated data from a data stream that is modulated by various schemes such as frequency shift keying (FSK). The system can be further designed to measure phase error and adjust internal clock to achieve phase lock with the demodulated data and track the data, and a numerically controlled oscillator (NCO) generates a recovered clock accordingly. The system may operate plesiochronously and be designed to operate at a nominal rate of a standardized data schemes and may require constant adjustments as deviations from the nominal, standardized rate occur.